1. Field of the Invention
The present invention relates to an information signal communication apparatus, method, and system, and more particularly to a process of modulating an information signal to be transmitted over a transmission path.
2. Related Background Art
In spread spectrum communications using direct spreading, an information signal (baseband signal) to be transmitted is spread modulated by using spread code series such as pseudo noise (PN) codes to generate a spread modulated signal having a bandwidth considerably broader than the baseband signal. This spread modulated signal is converted into a radio frequency (RF) signal by using phase shift keying (PSK), frequency shift keying (FSK) or the like and transmitted to a reception side.
On the reception side, the received RF signal is demodulated to the spread modulated signal before the transmission, and thereafter this spread modulated signal is converted into the original baseband signal before the transmission, by correlating (i.e., reverse spread modulating) the spread modulated signal with the spread code series used for the transmission.
Such spread spectrum modulation makes the bandwidth of a transmission signal considerably broader than that of an information signal. Therefore, under the conditions that the bandwidth of a transmission path is constant, for example, the amount of information to be transmitted becomes vary small as compared to conventional radio communications and only a low transmission rate can be realized.
As a method for solving this problem, there is a method called code division multiplex. With this method, an information signal to be transmitted is first divided into a plurality of parallel data sets, and respective data sets are spread modulated by using a plurality of different spread code series. These spread modulated data sets are multiplexed and converted into an RF signal to be transmitted. This method realizes high speed data transmission even under the conditions that the bandwidth of a transmission path is constant.
This code division multiplex is, however, associated with the following problems. For example, the more the number of data sets to be multiplexed (hereinafter called a multiplex number) is increased to transmit a larger amount of information, the more a phenomenon called multi-path fading becomes likely to occur. This phenomenon lowers the power level of a received signal through interference between a direct wave and a reflected wave having a phase different from the direct wave. Because of this phenomenon, as the multiplex number is increased, errors in transmission signals increase which result in communication interference or failure.
Furthermore, under the transmission path conditions that the amount of noises mixed with a transmission signal changes occasionally, it is necessary to set the multiplex number so as to match such conditions. However, since it is difficult to detect mixed noises during communications, the control of the information amount matching the transmission path conditions is very difficult. Still further, it is also very difficult to control to adaptably change the relationship between a transmission signal error rate and a transmission rate in accordance with the significance factor of a transmission signal.
An object of the present invention is to solve the above-described problem.
Another object of the present invention is to provide an information signal communication apparatus capable of controlling the modulation process of an information signal in accordance with the significance factor of an information signal to thereby optimize a transmission error rate and a transmission rate.
According to a preferred embodiment achieving the above objects, the invention discloses an information signal communication apparatus, comprising: (a) input means for inputting an information signal; (b) modulating means for modulating the information signal input from the input means; (c) discriminating means for discriminating a significance factor of the information signal input from the input means; (d) control means for controlling a modulation process of the modulating means in accordance with a discrimination result of the discriminating means; and (e) transmitting means for transmitting the information signal modulated by the modulating means.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) receiving unit for receiving an information signal modulated in accordance with a preset significance factor; (b) discriminating means for discriminating a modulation process given to the information signal; and (c) demodulating means for demodulating the information signal in accordance with a discrimination result of the discriminating means.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) input means for inputting at least an image signal, a control signal, and an information signal other than the image signal and the control signal; (b) modulating means for modulating a signal input from the input means; and (c) switching means for switching between modulation processes of the modulating means, in accordance with each of the image signal, the control signal and the information signal input from the input means.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) image pickup means for generating an image signal from a picked-up optical image of a subject; (b) modulating means for modulating the image signal generated by the image pickup means; (c) transmitting means for transmitting the image signal modulated by the modulating means; and (d) control means for controlling the image pickup means in accordance with an external control signal subjected to a modulation process, wherein the modulating means modulates the external control signal by a modulation process different from a modulation process of the control signal.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) receiving means for receiving an image signal output from an external unit having an image pickup unit, the image signal having been subjected to a predetermined modulation process; (b) discriminating means for discriminating a modulation process of the image signal received with the receiving means; (c) modulating means for modulating a control signal in accordance with a discrimination result of the discriminating means, the control signal controlling the image pickup unit; and (d) transmitting means for transmitting the control signal modulated by the modulating means, wherein the modulating means modulates the control signal by a modulation process different from a modulation process of the image signal.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) input means for inputting an image signal; (b) converting means for converting the image signal input from the input means into frequency components to divide the image signal into a plurality of frequency domains; (c) modulating means for modulating the image signal converted by the converting means for each frequency domain, the modulating means using a different modulation process for each frequency domain of the image signal; and (d) transmitting means for transmitting the image signal modulated by the modulating means.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) input means for inputting an information signal; (b) transmitting means for transmitting the information signal input from the input means; (c) discriminating means for discriminating a significance factor of the information signal input from the input means; and (d) control means for controlling a transmission rate of the information signal in accordance with the significance factor of the information signal discriminated by the discriminating means.
According to another preferred embodiment, the invention discloses an information signal communication apparatus, comprising: (a) input means for inputting an image signal; (b) compression means for compression coding the image signal selectively using first and second compression processes, the first compression process compression coding the image signal in a predetermined unit and the second compression process being different from the first compression process; (c) modulating means for modulating the image signal compression coded by the compression means, by using a modulation process corresponding to the first or second compression process; and (d) transmitting means for transmitting the image signal modulated by the modulating means.
Still another object of the present invention is to provide an information signal communication system capable of controlling the modulation process of an information signal in accordance with the significance factor of an information signal to thereby optimize a transmission error rate and a transmission rate.
According to a preferred embodiment achieving the above object, the invention discloses an information signal communication system, comprising: (a) image pickup means for generating an image signal from a picked-up optical image of a subject; (b) modulating means for modulating the image signal generated by the image pickup means; (c) transmitting means for transmitting the image signal modulated by the modulating means; and (d) control means for controlling the image pickup means in accordance with a control signal subjected to a modulation process, wherein the modulating means modulates the control signal by a modulation process different from a modulation process of the control signal.
A still further object of the present invention is to provide an information signal communication method capable of controlling the modulation process of an information signal in accordance with the significance factor of an information signal to thereby optimize a transmission error rate and a transmission rate.
According to a preferred embodiment achieving the above object, the invention discloses an information signal communication method, comprising: (a) an input step of inputting an information signal; (b) a modulation step of modulating the information signal input at the input step; (c) a discrimination step of discriminating a significance factor of the information signal input at the input step; (d) a control step of controlling a modulation process at the modulation step in accordance with a discrimination result by the discrimination step; and (e) a transmission step of transmitting the information signal modulated at the modulation step.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) a reception step of receiving an information signal modulated in accordance with a preset significance factor; (b) a discrimination step of discriminating a modulation process given to the information signal; and (c) a demodulation step of demodulating the information signal in accordance with a discrimination result at the discrimination step.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) an input step of inputting at least an image signal, a control signal, and an information signal other than the image signal and the control signal; (b) a modulation step of modulating a signal input at the input step; (c) a switching step of switching between modulation processes at the modulation step in accordance with each of the image signal, the control signal and the information signal input at the input step; and (d) a transmission step of transmitting a signal modulated at the modulation step.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) an image pickup step of generating an image signal from an optical image of a picked-up subject; (b) a modulation step of modulating the image signal generated at the image pickup step; (c) a transmission step of transmitting the image signal modulated at the modulation step; and (d) a control step of controlling the image pickup step in accordance with an external control signal subjected to a modulation process, wherein the modulation step modulates the external control signal by a modulation process different from a modulation process of the control signal.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) a reception step of receiving an image signal output from an external unit having an image pickup unit; (b) a discrimination step of discriminating a modulation process of the image signal received at the reception step; (c) a modulation step of modulating a control signal in accordance with a discrimination result by the discrimination step, the control signal controlling the image pickup unit; and (d) a transmission step of transmitting the control signal modulated by the modulation step, wherein the modulation step modulates the control signal by a modulation process different from a modulation process of the image signal.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) an input step of inputting an image signal; (b) a conversion step of converting the image signal input at the input step into frequency components to divide the image signal into a plurality of frequency domains; (c) a modulation step of modulating the image signal converted at the conversion step at each frequency domain, the modulation step changing a modulation process of the image signal at each frequency domain; and (d) a transmission step of transmitting the image signal modulated at the modulation step.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) an input step of inputting an information signal; (b) a transmission step of transmitting a significance factor of the information signal input at the input step; (c) a discrimination step of discriminating a significance factor of the information signal input at the input step; and (d) a control step of controlling a transmission rate of the information signal in accordance with the significance factor of the information signal discriminated at the discrimination step.
According to another preferred embodiment, the invention discloses an information signal communication method, comprising: (a) an input step of inputting an image signal; (b) a compression step of compression coding the image signal by selectively using first and second compression processes, the first compression process performing compression coding of the image signal in a predetermined unit and the second compression process being different from the first compression process; (c) a modulation process of performing a modulation process of the image signal compression coded at the compression step, the modulation process corresponding to the first or second compression process; and (d) a transmission step of transmitting the image signal modulated at the modulation step.
Still other objects of the present invention and the advantages thereof will become fully apparent from the following detailed description of the embodiments.